Wheel hubs for use in coupling a tire to a vehicle axle are well known. By way of illustration, a conventional boat trailer utilizes a fixed axle secured to a trailer frame. A wheel assembly is coupled to the axle by use of a wheel hub. The wheel hub employs a bearing assembly to allow free rotation of the hub in relation to the axle. Thus, the wheel assembly, which includes the tire, permits transportation of the boat trailer over a road when trailered by an automobile. The conventional wheel hub employs bearings, namely an inner and outer bearings with an associated inner and outer race, which permits rotational movement in relation to the axle.
As with any friction producing components, it is imperative that the bearings are lubricated in order to prevent premature wear. Typically, a bearing grease is used which liquefies during bearing rotation for use in lubricating the bearings. The grease is sealed within the hub by use of an oil seal positioned along an inner side surface of the hub, and a bearing cap positioned along an outer side surface of the hub. The seals are used to prevent liquified grease from escaping the hub joint.
Thus the integrity of the oil seal and hub cover is critical to prevent loss of grease. Absence of a lubricant can quickly lead to catastrophic failure of the bearings causing hub disengagement of the axle, which can result in wheel assembly loss and the associated dangerous scenario of property and possibly life endangerment. For instance, a trailer carrying a heavy load such as a 25 foot boat, will quickly heat up a bearing that is not properly lubricated. Should the bearing fail, the bearing and race will typically disintegrate with a likely result of the hub and wheel detaching from the axle of the trailer. Boat trailers present an excellent example of premature wear as a boat trailer is typically inserted into water for loading or unloading of the boat. Should there be a failure of the hub seal, water is allowed to enter the hub resulting in the premature wear. In addition, should the water be saltwater, bearing disintegration is greatly enhanced since rust forming on the bearing surfaces will operate to destroy the bearings with very short use.
In light of the above numerous attempts have been made in order to prevent loss of bearing lubricant Many prior art wheel hub devices maintain pressurized grease within the hub. A very successful system consists of a modified hub cap having a grease fitting with a spring which visually indicates that grease has been inserted into the hub. However, should the hub seal fail, the assembly will actually facilitate grease being pushed through the seal. Should the spring jam, even if the bearing indicator illustrate that grease is prevalent in the seal, it may be providing a false indication. In addition, a slow leak will allow grease to be inserted into the hub and upon liquification during operation the seal could allow the liquified grease to easily escape.
Unfortunately, a spring loaded system to pressurize grease into the hub results in an excess amount of grease injected into the hub for proper operation. This results in an obvious waste of grease for only the bearing rollers must be lubricated. Thus, the amount of grease necessary is simply a coating over the bearing rollers. The spring loaded system advocates that should a seal leak, the user need simply pump more grease into the wheel hub on a continuous basis. Of course, the grease continues to leak from the wheel hub because the breach in the seal remains. For instance, a person may check a hub and insert grease into the hub before taking the trailer on the road. Once the trailer reaches operating speed, the liquified grease may easily escape. Should the operator back trailer into a lake, for purposes of unloading a boat, grease that has escaped from the hub and remains on the trailer will be exposed to the water.
Prior art patents directed to wheel bearing lubricators teach that the release of grease into the water is advantageous. Vangalis, U.S. Pat. No. 3,785,706, discloses a hub cap of transparent plastic which is closed at the outer end and contains a spring-backed piston for applying pressure on lubricant grease in the hub cap for yielding when the lubricant expands. The hub cap has two small vents, one for permitting lubricant to escape when expansion is excessive and the other to vent the enclosed portion of the hub behind the piston to atmospheric pressure.
Ploeger, U.S. Pat. No. 4,190,133, discloses a wheel bearing pressure lubricator for hubs subject to periodic submersion in water. The device includes a piston for relieving excess lubricant pressure and a piston position indicator providing a visual indication when the piston is in hub filled position and when the piston is in a no pressure position at which the piston ceases to apply pressure to the lubricant in the hub.
The adverse environmental impact of petroleum product contamination of natural water environments is well known. The constant expulsion of grease into natural waters by the prior art bearing lubrication systems will have a cumulative negative impact on the environment. In the year 2001, the National Marine Manufacturers Association estimated that 7,564,900 boat trailers were in operation, a significant number of which are continuously expelling grease into natural waters. Should the water be a reservoir for drinking water, even a few drops of oil can result in system contamination. However, it is well known that any oil in water has an adverse effect to wildlife.
Total estimated retail expenditures on boating totaled $25,593,409,000 in 2001. Recreational boating in the United States is an ever-growing industry, a trend which is increasingly at odds with environmental concerns. The continued water pollution by leaking wheel hubs is unnecessary and preventable, and that there remains a need for an “environmentally friendly” system of bearing maintenance.
Thus, what is lacking in the art is a positive indication of hub and oil seal integrity to indicate availability of bearing grease within the hub which does not release grease into the environment.